1. Sprinkle the chicken pieces on both sides with the salt and set aside at room temperature for 5 minutes or so.
2. Meanwhile, in a heavy 5- to 6-quart casserole, heat 2 tablespoons of the oil over moderate heat until a light haze forms above it.
3. Drop in the ginger and stir it for 20 or 30 seconds, then add the onion slices and, stirring frequently, cook for about 5 minutes, or until they are soft and transparent but not brown. With a slotted spoon, transfer the ginger and onion to a plate and set aside.
4. Brown the chicken in the oil remaining in the casserole, adding 2 tablespoons more oil if necessary. Turn the pieces frequently with tongs and regulate the heat so that the chicken colors richly and evenly without burning.
5. Return the ginger and onion to the pan, pour in the water and bring to a boil over high heat. Reduce the heat to low and simmer, partially covered, for 40 to 50 minutes, or until the chicken is tender but still intact.
6. Remove the pan from the heat, stir in the pepper or spinach leaves and serve at once from a heated tureen or in individual soup plates.
